1. Field of the Invention
The present invention relates to an output circuit and, more particularly, to an output circuit employed in a signal transmission system, a semiconductor storage device, or the like.
2. Description of the Related Art
Recently, it has become necessary to transfer signals between circuits that are different from each other in terms of a power supply voltage and are included in large-scale integration circuits (LSI circuits) constituting an information processing system, or between circuits included in one LSI circuit. However, when signals are transferred between such circuits different from each other in terms of a power supply voltage, it has been difficult for an output circuit to transmit signals to a receiver circuit with an optimal common-mode voltage. Furthermore, in order to cope with a recent demand for high-speed transmission, the problems of a loss of a high-frequency component and reflection of a signal must be solved.
Specifically, a circuit capable of operating at a high speed so as to meet a recent request for high-speed transmission often includes, for example, transistors that can operate at a high speed but that can resist only a low voltage. Further, assuming that such a circuit is connected to a circuit that is different from the circuit in terms of, for example, a power supply voltage, a signal amplitude, or a common-mode voltage, if a voltage exceeding a voltage which the transistors can resist is applied to the circuit, the circuit may be broken.
The prior art and the problems associated with the prior art will be described in detail later with reference to accompanying drawings.